During the past year research efforts under this project were concentrated on Entamoeba histolytica in three study areas: 1) nutrition of the amebae in axenic culture, 2) mechanisms involved in production of amebal lesions in experimental animals, and 3) the endogenous viruses of this parasite, their further characterization, and the role they may play in influencing amebal virulence. These studies will be continued next year. Additionally, special attention will be given to development of a medium for isolation of Giardia lamblia from human feces.